U.S. Pat. No. 4,626,250 depicts, in FIG. 18, a sheath for a male external catheter in which an adhesive coating 50 is disposed along the inner surface of the sheath's cylindrical body for adhesively securing the sheath to the penile shaft of a user. As indicated in FIG. 19, the sheath is supplied to the user in rolled form with the adhesive layer interposed between successive coils or turns and then, as the sheath is unrolled, the adhesive, which remains on the sheath's inner surface, is advanced into contact with the wearer. Effective application of the device obviously requires that the adhesive coating refrain from adhering to the sheath's outer surface as the sheath is unrolled and, as explained in the patent (column 10), any suitable release coating or interliner as well known in the tape industry and in other fields may be used for that purpose. In the example given, a silicone coating is provided on the sheath's outer surface to keep the adhesive 50 from adhering to that surface when the sheath is unrolled.
A common method for providing such a silicone coating during sheath manufacture is by a dipping step since other techniques, such as spraying, provide less control and create other problems in the workplace. Such problems are not entirely avoided even when a dipping process is used, since silicone tends to migrate even under carefully controlled working conditions, causing complications with equipment and silicone exposure to other surfaces not intended to be treated. Furthermore, the silicone baths into which catheter sheaths may be dipped tend to be very sensitive to ambient conditions. For example, under conditions of relatively high humidity, the useful life of such a bath may be greatly reduced, resulting in substantial material waste and increased manufacturing costs. Sheaths treated with silicone that has been adversely affected by humidity may be rendered unusable because the release coatings may not cure properly if at all. Furthermore, even after application and curing, silicone release coatings applied by dipping may prove troublesome, resulting in discoloration, blushing, flaking, cracking, and loss of release properties.
Some of these problems are summarized in International Patent Application PCT/DK85/00068, published February 13, 1986. There, reference is made to the laborious prior art manufacturing procedures that first require forming of a catheter's body portion by immersing a mandrel into a latex solution, followed by rinsing and drying prior to the application of a silicone rubber layer, followed by curing of the silicone rubber layer before application of an adhesive which is then expected to transfer from the silicone rubber layer to the inside surface of the catheter when the product is rolled during the final stage of manufacture and later unrolled at time of use. Reference may also be had to U.S. Pat. No. 4,475,910 for discussion of the adhesive-transfer procedure.
Application PCT/DK85/00068 further discloses a procedure which eliminates the need for a silicone dipping step and thereby avoids many of the problems inherent in such a procedure. Unfortunately, the purported improvement is itself relatively complex, involving the application of an adhesive strip to one surface of the sheath and a silicone-bearing strip to the sheath's opposite surface. Means must be provided for inflating and deflating the sheath during processing in order to bring the strips into contact with the sheath's opposite surfaces at precise locations which will permit the adhesive and release coatings to register properly when the sheath is rolled in the final stage of manufacture.